The manufacturing process for producing elastomeric articles from natural or synthetic rubber latex involves a curing step during which cross-linking or vulcanization through sulfur groups occurs between the polymer units. Conventional processes for making elastomeric articles from natural or synthetic latex typically involve preparing a latex dispersion or emulsion, dipping a former in the shape of the article to be manufactured into the latex and curing the latex while on the former. Desirable properties of certain elastomeric articles such as tensile strength are substantially affected by the cross-linking and curing stages of the manufacturing process.
The use of vulcanizing or sulfur cross-linking accelerator compounds in the manufacture of rubber articles is well-known. Conventional vulcanization accelerators include dithiocarbamates, thiazoles, guanidines, thioureas, amines, disulfides, thiurams, xanthates and sulfenamides. The use of vulcanization accelerators in the manufacture of polyisoprene rubber is disclosed in D'Sidocky et al., U.S. Pat. No. 5,744,552 and Rauchfuss et al., U.S. Pat. No. 6,114,469. Certain fields in which elastomeric articles are needed, such as the medical field, utilize specific types of equipment and processing techniques which accommodate the specific performance and regulatory requirements of the particular article produced.
The use of natural rubber latex in the manufacture of certain articles such as medical gloves has been associated with disadvantageous properties, such as allergic reactions believed by some to be caused by natural proteins or allergens present within the natural rubber latex and the final product. Of increasing interest in the medical field, particularly in the field of gloves, are synthetic elastomeric products and manufacturing processes which altogether reduce, or altogether avoid, the likelihood of potential adverse reactions of the user or wearer.
Synthetic elastomeric polyisoprene articles such as gloves are known and are of interest in the art as an alternative to the use of natural latex. Commercially available synthetic gloves include those elastomers composed of polychloroprene (neoprene), carboxylated acrylonitrile butadiene (nitrile), styrene-isoprene-styrene/styrene-ethylene-butylene-styrene block co-polymers, polyurethane, and polyisoprene. Polyisoprene is one of the most preferred polymers due to its chemical similarity to natural rubber as well as its physical properties such as feel, softness, modulus, elongation and tensile strength. One such polyisoprene glove is commercially available from Maxxim Medical (Clearwater, Fla.).
A majority of glove manufacturing processes are water-based dipping systems. It is known that solvent-based systems are possible for polyisoprene, although such systems are poorly suited for the manufacture and molding of elastomeric articles for medical applications. One difficulty in the field of gloves, for example, is the design of processes and materials which will produce a thin elastomeric article having desirable properties such as high tensile strength. Another disadvantage of solvent-based systems is solvent toxicity. Process and materials which would obviate or reduce the need for the use of toxic solvents while at the same time yielding a product having desirable properties for medical applications are thus still being explored.
Accordingly, there exists a need in the medical device field for improved manufacturing processes for making synthetic elastomeric articles. Especially desirable would be processes which can produce polyisoprene articles, such as surgical gloves, which possess the desirable properties found in the natural rubber counterpart, while at the same time permitting economical and cost-effective manufacturing.